Add support for basic scaling of horizontal gaps

FIX: Improve the way enormously long (non-wrapped) lines are displayed by making sure they
stay shorter than the maximal pixel size the browser's CSS engine can handle.

Closes #1448

Author: marijnh

demo/demo.ts

@@ -1,11 +1,13 @@
 import {EditorView, basicSetup} from "codemirror"
-import {javascript} from "@codemirror/lang-javascript"
 
-;(window as any).view = new EditorView({
-  doc: 'console.log("Hello world")',
-  extensions: [
-    basicSetup,
-    javascript(),
-  ],
+let doc = ""
+for (let i = 0; i <= 1245526; i++) doc += String.fromCharCode("a".charCodeAt(0) + Math.floor(Math.random() * 26))
+
+let view = (window as any).view = new EditorView({
+  doc,
+  extensions: basicSetup,
   parent: document.body
 })
+
+console.log("---")
+view.dispatch({selection: {anchor: view.state.doc.length}, scrollIntoView: true})